This invention relates to the field of laser calibration, and more particularly to systems for positioning a focused laser beam over a processing area with high precision.
In many material processing applications it is necessary to position a focused laser beam over a processing area with very high precision. Various prior art methods have been proposed to determine the position of a moveable laser beam.
One method uses a charge coupled device (CCD) camera and a small portion of the processing beam to indirectly measure changes in the beam position. This approach only works well as a correction for small changes to a substantially static beam since the split off portion of the beam is focused through a different lens than the one used for processing.
Another method monitors scattered light from the work piece with a CCD camera to determine the actual position of the beam.
Yet another method processes a test part with an array of features; measures the processed part and compares the actual feature positions with the planned locations; and uses the difference to calculate a table of correction factors.
Further, beam profilers often use a moving aperture/detector assembly to determine the shape of a laser beam, but these devices are not concerned about referencing the beam shape to the coordinate system of a material processing machine, for example.
It is an object of the present invention to improve laser beam position calibration methods and systems.
It is an object of the present invention to provide an automatic and consistent laser beam position calibration method and system.
It is an object of the present invention to provide a method and system for determining scanner coordinates to position a laser beam.
In accordance with one aspect of the present invention there is provided a method of correlating scanner position coordinates of a laser scanner with beam position coordinates of a focused laser beam to improve position accuracy of the focused laser beam, said method comprising the steps of: scanning the focused laser beam over a region of interest on a work surface; detecting the focused laser beam received at a photodetector contiguous with the work surface, wherein a location of the detected focused laser beam produces beam position coordinates; and forming scanner position versus beam position data by creating associations between beam position coordinates and scanner position coordinates corresponding to the position of the laser scanner when the focused laser beam is detected.
In accordance with another aspect of the present invention there is provided a method of improving precision when positioning a focused laser beam, said method comprising the steps of: scanning the focused laser beam over a region of interest on a work surface; detecting the focused beam received at a photodetector contiguous with the work surface, wherein a location of the detected focused laser beam produces beam position coordinates; forming scanner position versus beam position data by creating associations between beam position coordinates and scanner position coordinates corresponding to a position of the laser scanner when the focused laser beam is detected; determining beam position coordinates for a desired position for the focused laser beam; and calculating desired scanner position coordinates that correspond with the desired position based on the scanner position versus beam position data.
In accordance with a further aspect of the present invention there is provided a method for determining laser scanner position coordinates to position a focused laser beam comprising the steps of: scanning the focused laser beam over an aperture on a work surface; monitoring power transmitted to through the aperture by the focused laser beam using a photodetector to generate scanner coordinate versus photodetector signal data; deriving from the scanner position versus beam position data, scanner coordinates corresponding to a position of the center of the aperture.
In accordance with yet another aspect of the present invention there is provided a method of determining the features of an aperture on a machining plane using a laser beam comprising the steps of: scanning the laser beam about the aperture on the machining plane; collecting light passing through the aperture on a detector to determine a profile of detector signal versus scanned beam position; and defining a threshold of the detector signal thereby defining scanned beam positions defining the edges of the aperture.
In accordance with an additional aspect of the present invention there is provided an apparatus for improving position accuracy of a focused laser beam comprising: a laser scanner having scanner position coordinates for scanning the focused laser beam over a region of interest on a work surface; a photodetector for detecting when the focused laser beam is received at the work surface, wherein a location of the detected focused laser beam produces beam position coordinates; and a data forming means for forming scanner position versus beam position data by creating associations between beam position coordinates and scanner position coordinates corresponding to the position of the laser scanner when the focused laser beam is detected.
In accordance with a further aspect of the present invention there is provided an apparatus for improving precision when positioning a focused laser beam comprising: a laser scanner having scanner position coordinates for scanning the focused laser beam over a region of interest on a work surface; a photodetector for detecting when the focused laser beam is received at the work surface, wherein a location of the detected focused laser beam produces beam position coordinates; a data forming means for forming scanner position versus beam position data by creating associations between beam position coordinates and scanner position coordinates corresponding to the position of the laser scanner when the focused laser beam is detected; and a position determining means for determining the beam position coordinates for a desired position for the focused laser beam and calculating desired scanner position coordinates that correspond with the desired position based on the scanner position versus beam position data.
In accordance with an additional aspect of the present invention there is provided an apparatus for determining laser scanner position coordinates to position a focused laser beam comprising: means for scanning the focused laser beam over an aperture on a work-surface; means for monitoring power transmitted through the aperture by the focused laser beam using a photodetector to generate scanner position versus beam position data; and means for deriving from the scanner position versus beam position data, scanner coordinates corresponding to the position of the center of the aperture.
In accordance with another aspect of the present invention there is provided an apparatus for determining the features of an aperture on a machining plane using a laser beam comprising the steps of: means for scanning the laser beam about the aperture on the machining plane; means for collecting light passing through the aperture on a photodetector to determine a profile of photodetector signal versus scanned beam position; and means for defining a threshold of the photodetector signal thereby defining scanned beam positions defining the edges of the aperture.